Synchronous (sync) replication is a business continuity process that mirrors data updates between two systems to prevent data loss and downtime. When sync replication is turned on for a production storage object, the system mirrors the data to a target system as part of handling write requests from an initiator, and only responds to the initiator after the writes have been persisted on both the source and target systems.
As data on the source and target sites are inherently different with ever changing inflight inputs/outputs (IOs), it is challenging to perform data verification for volumes that are in active sync replication mode. One solution is to suspend host IOs followed by draining the inflight IOs to create a pair of synchronized snap sets when the sync replication process becomes enabled. However, the period of suspending and draining IOs and creating snap sets may cause major IO latency hiccups for applications, which may not be practical or desirable in real customer environments where steady/low IO latency requirements are critical.